Conventional receivers in optical communication systems are usually designed to maximize receiver sensitivity. This approach originates from telecommunication applications, where very weak optical signals have to be recovered from noise. The detected signals are amplified and processed in the electronic domain. The ability to detect very weak signals is a much more important design consideration for telecommunications applications compared to the power dissipation of the receiver. This is especially relevant in long-haul communications systems, where improved receiver sensitivity implies that a longer transmission distance can be achieved.
In optical interconnects for data center networks, the transmission distance of data is of less concern, and end-to-end power consumption of the link is the primary design parameter of the system. This implies different requirements for the receiver. Data-centers usually contain a large number of servers (e.g., up to several hundred thousand) clustered in groups. These servers and clusters are connected to each other via a communication network. The data capacity of this interconnection network depends on the performance of the data center. As a rule of thumb, 0.1 Byte/sec of communication capacity is required per Flop per second performance. As the overall performance of data-centers is the order of Petaflops/per second, the overall data-capacity of a single data-center interconnect network is on the order of petabits/sec. More importantly, it is well known that the performance of data-centers increases by roughly a factor 1000 per 10 years, and as a result of this scaling, the performance of the data-center communication network will need to increase proportionally. Because of the large data capacity requirement of the data center communication network, optical communication is rapidly evolving as the dominant technology for intra-data-center communications.
However, investigations have shown that if conventional optical receivers (e.g., telecommunications receivers with trans-impedance amplifier (TIA) front ends) are used in such data center networks, the power consumption can be prohibitive. For example, one 10-year projection estimated 100 MW dissipation by the optical network of a data center.
Accordingly, it would be an advance in the art to provide optical receivers suitable for such data center network applications.